Langer Heinrich Uranium Mine, Namibia
Langer Heinrich Uranium Mine is an open-pit mine in the Namibia Desert, about 80km east of Walvis Bay, Namibia. The uranium deposit was discovered in 1973 and the mine was re-launched for operations in 2007 after remaining unused for almost seven years.
Langer Heinrich is owned and operated by Paladin Resources. The company acquired the property from Aztec Resources in 2002. Paladin sold 25% stake in the project to CNNC Overseas Uranium Holding in July 2014.
The mine produced 2.7Mlb of uranium in 2008-09. Mining operations have been contracted to Karibib Mining and Construction Company.
A stage-two expansion programme was completed in June 2009, which involved an investment of $50m to increase the mine's production to 3.7Mlb/year.
The stage-three expansion completed in March 2012 increased the annual production to 5.2Mlb of U3O8. Paladine also started a bankable feasibility study for the stage-four expansion programme.
The mine lies within a 15km-long tertiary paleo-drainage system that contains seven contiguous mineralised zones. Characterised by calcrete, the deposit hosts valley-fill sediments. Depending upon the width of the valley, mineralisation ranges from 1m to 30m in thickness and 50m to 1,100m in width near the surface.
Uranium is found within carnotite, an oxide that contains uranium and vanadium. The carnotite occurs as thin films lining grains, fracture planes and cavities or as disseminations.
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As of June 2014, the mine contained 22.4Mt of measured resources at an assumed grade of 0.055% U3O8. The cut-off grade is 250ppm. Indicated resources are estimated at 67Mt. Inferred resources were estimated at 17.6Mt grading at 0.06% U3O8. The total ore reserves including proven, probable and stockpiles were 103.8t of 0.052% grade, containing 53,917t of U3O8.
The mine can produce up to 1,180t of uranium oxide concentrate from 1.5Mt of calcrete-hosted ores per year. Ores are processed using conventional methods including ore beneficiation, alkaline leaching, counter-current decantation, ion exchange, precipitation and calcining. Agglomerates are broken down into individual grains through crushing and scrubbing.
During the process uranium minerals are separated from the surface of the grains. High-grade fines or leach feed are separated using cyclones and screen methods from barren discard material.
Once thickened, the leach feed slurry is conditioned with carbonate and bi-carbonate before it is heated and pumped to the leach circuit. The slurry is then fed through a counter current decantation (CCD) circuit, where high-grade uranium solution is separated from solids.
After undergoing additional clarification, the solution is pumped through fixed bed ion exchange (IX) columns. In the IX columns uranium is recovered on to resin. The uranium is removed from resin before being precipitated as sodium diuranate. After being re-dissolved with sulphuric acid, the uranium is further precipitated with hydrogen peroxide. The product delivered is dewatered, dried and stored as uranyl peroxide.
The stage-two expansion, which was undertaken to boost production, involved upgrading the recycle crushing circuit and feed conveyor, expanding the cyclone circuit and installing a new pre-leach thickener, additional leach capacity, heaters, high-density thickeners and IX columns.
It also involved the expansion of the new drier, including the feed arrangement, increasing the capacity of reagent dosing, the construction of additional motor control centre (MCC) buildings and upgrading the tailings disposal.
A stage-three expansion began in June 2009 and was completed in March 2012. The production commenced in April 2012.Originally scheduled for completion in January 2011, the project was delayed due to late deliveries of boilers and IX columns.
The feasibility study for stage-four expansion will investigate the viability of setting up a new 8.7Mlb/year production plant adjacent to the existing one. It will also investigate the potential of heap leaching or upgrading the material / mineralised waste rock with a below cut-off grade to recover an additional 1.3Mlbs of uranium. The expansion will not occur until the substantial increase in incentive uranium price.
By mid 2009 the mine had exceeded stage-one production of 2.6Mlbs/year. The production rate was achieved throughout the year, with almost no interruptions related to the execution of the stage-two expansion. To deliver the additional feed required for the stage-two expansion the mining fleet was increased. Mining was exhausted in the initial two pits and progressed towards Pit D in the west and Pit A in the north.
With the completion of stage-three expansion, the production totalled 5.29Mlb/year.
In 2009 Langer Heinrich Uranium received Environmental Management System (EMS) certification in compliance with ISO 14001:2004. The certification applies to the entire mining operation, including open-pit mining and production of uranium oxide in Namib-Naukluft National Park.
In the last quarter of 2012, stage four received Environmental Impact Assessment (EIA) approvals from the Namibian Government.